The broad long-term goal of the proposed research is to understand the functions of 17beta-estradiol (estrogen; E2) and estrogen receptors (ERs) in the developing nervous system and to determine to what extent environmental estrogens influence these functions. E2 influences the development and function of many regions of the brain in both males and females. Thus, it is possible that other estrogenic compounds can impact development of the brain. Environmental estrogens, also known as "endocrine disrupters," are a diverse group of compounds that can mimic or antagonize the normal actions of E2. The extent to which environmental estrogens impact the developing nervous system is unclear. Proposed experiments employing primary cultures of neonatal rat cerebellar neurons and the developing cerebellum as models will address the following Specific Aims-Specific Aim 1: Determine whether E2 modulates cellular signaling in developing cerebellar neurons through rapid, non-genomic actions on MAPK signal transduction; Specific Aim 2: Determine the networks of estrogen responsive genes whose expression is modulated by E2 in cerebellar neurons; Specific Aim 3: Determine to what degree representative environmental estrogens mimic or inhibit the effects of E2 in developing cerebellar neurons. Specific Aims 1 & 2 test the hypothesis that E2 normally functions in developing neurons by rapidly modulating the activity of MAPK signaling, and also through genomic ER-mediated mechanisms which together, modify expression of discrete networks of gene products. Specific Aim 3 will test the hypothesis that environmental estrogens influence developing neurons by modifying both MAPK signaling and genomic ER-mediated mechanisms, which results in altered networks of expressed genes. All three Specific Aims will be addressed through experiments using activation-state specific antisera to determine E2-mediated signaling pathways and by cDNA array and RT -PCR analysis of E2-responsive gene expression. From these results a neuronal "E2-signature cDNA array" will be developed and used in Aim 3 to determine how environmental estrogens influence E2-responsive gene expression in these developing neurons.